2. The N.F.L. playoffs got underway this weekend with Wild Card games — which have produced the eventual Super Bowl winners three times since 2010. Our coverage is here. There’s plenty of action off the field, too. In the next few days, team owners will begin considering bids by the San Diego Chargers, the Oakland Raiders and the St. Louis Rams to relocate to Los Angeles, where the airwaves glitter with gold.

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CreditPetar Kujundzic/Reuters

3. Global markets are bracing for the possibility of another rocky ride after concerns about China’s slowing economy last week set off plunges in Chinese stocks and routs around the world. U.S. markets lost 6 to 7 percent for the first trading week of the year, their worst start ever. Our money columnist has ideas about how you can handle your own investments.

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CreditPoras Chaudhary for The New York Times

4. Need a reminder that the world is beautiful? Check out “52 Places to Go in 2016,” even if you don’t plan to travel any further than your armchair.

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CreditDoug Mills/The New York Times

5. President Obama began the final year of his term with a concerted push for gun control, weeping for the 20 first-graders killed at an elementary school in 2012 as he announced new executive actions. When he gives his last State of the Union Address on Tuesday (9 p.m. Eastern), a seat in the House gallery will be left empty to symbolize deaths from gun violence.

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CreditScott Olson/Getty Images

6. The race to succeed Mr. Obama roared on. Bernie Sanders and Donald Trump topped polls in New Hampshire. Lena Dunham, the star of “Girls,” took over Hillary Clinton’s Instagram account. Many Republican candidates gathered in South Carolina for a poverty forum. Ted Cruz was wrapping up his six-day bus tour of Iowa, and Mr. Trump had overflow crowds in South Carolina and New Hampshire. The next Republican presidential debate is Thursday (9 p.m. Eastern) on Fox Business Network.

8. An armed group’s takeover of a federal wildlife preserve in Oregon enters its second week. The group’s leader, Ammon Bundy, said he was “not yet” ready to take the sheriff’s offer for safe passage out of the refuge. The situation is prompting a renewed focus on how the U.S. monitors antigovernment groups.

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CreditSam Yeh/Agence France-Presse — Getty Images

9. Seismic readings showed that North Korea’s claimed H-bomb test was probably only an enhanced atomic bomb. But the test disrupted relations between an exasperated U.S. and China, the North’s lone backer, which has put up with the Kim dynasty’s bellicose leadership for decades to avoid a state collapse that would cause chaos for China’s northeast.

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CreditMax Whittaker for The New York Times

10. Looking ahead, the Supreme Court hears arguments Monday in a California case challenging mandatory dues in public unions brought by 10 teachers, including the one pictured above. The court’s decision is expected by June. “It’s scary,” a union expert said, especially given that “most of the growth in the labor movement over the last few decades has been in the public sector.”

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Video

Each year, the American Physical Society awards prizes to research videos at the meeting of its fluid dynamics division. Here are some excerpts.Published OnDec. 21, 2015